Chlorine dioxide is widely used as a bleaching chemical and is known to be produced by reducion of sodium chlorate in an acid aqueous reaction medium. The reaction whereby chlorine dioxide is formed, is represented by the equation: EQU ClO.sub.3.sup.- +Cl.sup.- +2H.sup.+ .fwdarw.ClO.sub.2.sup.- +1/2Cl.sub.2 +H.sub.2 O
Generally, therefore, chlorine is co-produced with the chlorine dioxide.
Processes are known wherein the chlorine so-produced is reduced chemically, for example, using sulphur dioxide or methanol, thereby producing chloride ions for the process in situ. Such processes employ sulphuric acid as the acid source, resulting in sodium sulphate by-product.
In addition, there have been suggestions in the art to use electrolytic procedures for the production of chlorine dioxide. In this regard, the applicants are aware of U.S. Pat. Nos. 3,904,495, 3,904,496, 3,920,801, 4,308,117, 4,324,635 and 4,456,510.
With the exception of the latter patent, in each instance, chlorine dioxide is produced in conjunction with chlorine from aqueous chlorate solution in the anode compartment of a multicompartment cell. In U.S. Pat. No. 4,456,510, an aqueous sodium chlorite solution is electrolyzed to produce chlorine dioxide.